Solvent refining of lubricating oils



Patented Feb. 22, 1944 2,342,362 SOLVENT REFINIgG LUBRICATING IL George G. Oberfell, Bartlesville, kla., assignor to Phillips Petroleum Company, acorporation of Delaware No Drawing. Refiled for abandoned application Serial No. 748,761, October 17, 1934. This application September 2, 1941, Serial No. 409,297

6 Claims. (01. 196-13) This invention relates to the improvement of lubricating oils by the process generally known as solvent extraction. More particularly it relates to the use of a nitrobutane as a selective solvent in the treatment of lubricating oils, particularly nitroisobutanes. This application is a refile of my abandoned application, Serial No. 748,761, filed October 17, 1934.

More specifically, it provides a new method and reagent whereby a lubricating oil of petroleum origin may be separated into two fractions, one more highly paraffinic in character than the initial oil, and one containing most of the asphaltic and undesirable constituents of the original oil.

It has long been known that certain liquids exert a preferential solvent action upon certain types of constituents ordinarily present in lubri eating oils of petroleum origin. Usually these solvents, when brought into contact with the oil, will extract or concentrate the asphaltic and sulfur compounds, aromatic hydrocarbons and the like, leaving an undissolved residue which, when freed from solvent, is superior in lubricating properties to the original oil. Certain other solvents,

however, like propane, will mix with the oil phase and even precipitate asphaltic materials from the mixture under some circumstances.

I have discovered that certain nitrated paraifin hydrocarbons will exert a selective solvent action upon the less desirable constituents of petroleum lubricating oils. By intimately mixing, for example, a nitrobutane with the oil at such temperatures that the mixture separates into two phases upon standing, there is obtained a solvent phase in which are concentrated most of the undesirable constituents of the oil, and an oil phase containing a lubricant more parafiinic than the original oil, with a certain amount of the solvent dissolved therein. When the solvent is removed from this oil phase, as, for example, by distilling it off under vacuum, there results a lubricating oil of improved quality and high viscosity index, i. e. ratio of high temperature to low temperature viscosity.

My process may be operated in many ways, and many factors may be varied within reasonable limits without departing from th spirit of the invention. For example, the ratio of the volumes of solvent'and of oil treated may be varied within considerable limits, depending upon the particular solvent used, the character of the oil, the degree of improvement which it is desired to effect, yield, temperature, and other factors. A single batch extraction may be used, or a series of extractions, or even continuous countercurrent extraction. Temperatures at which the extraction is carried out may also vary, and the oil treated may be diluted if desired, for example,

with low boiling hydrocarbons, prior to the extraction step. A'cid treating or dewaxing of the oil may be used either preceding or following the extraction.

The nitrated parafiin hydrocarbons which I use in my process may contain anywhere from three to eight carbon atoms. In general, they may be formed by conducting a paraffin hydrocarbon and nitric acid vapor through a tube at high temperatures. The method of production of these compounds, however, forms no part of my invention. As typical of such compounds. I may mention l-nitroisobutane and Z-nitroisobutane, but other nitrobutanes and nitrated paraffin hydrocarbons will also be found suitable for my process under the proper operating con ditions.

As an exampleof the operation of the process, a typical Mid-Continent long residuum bright stock of 100 seconds Saybolt viscosity at 210 F. was treated with land 2-nitroisobutane with the results shown in the following table.

Table I 100 F. 210 F. f viscosity viscosity Viscosity Sp. gr. A. P I. gg g on on seconds seconds index 78 F gravity original Saybolt Saybolt Oil Original 1, 410 100 89782 25. 0

t ri fi i ii'gggb gglzi fl .1 1, 714 132 106 89195 26. 5 69. 2 From 2-nitrolsobutane 605 112 91 89573 25. 3 71. 4 Extra t 2 F lf l n iggg oifizae e? 1, 244 83- 7 60 92278 21. 8 30. 8 From Z-nitroisobutzme ,298 86 61 90319 24. 2 28. 6

In the above examples, the volume of nitroparamn used was equal to about twice the volume of oil treated, and the temperature of extraction approximately 70 F. The raffinate is that portion of the oil of lesser solubility in the nitroparaflin, and the viscosity index is an arbitrary scale for measuring the character of a lubricating oil oi petroleum origin (Dean and Davis, Oil & Gas Journal, March 31, 1932, p. 92).

thene base oils a much lower value.

In an attempt to determine optimum temperatures for an approximately thirty per cent removed by an extraction, using two volumes of nitrobutane to one of oil, refractive indice of the various phases were measured at'different temperatures. From these, the amount of oil in any phase could be determined. Chlorex extraction was used as a comparative standard on amounts extracted.

. InTable II are presented values for the refractive -indices of various extraction agents and bright stock. Table III gives values for therefractive indices of the oiland solvent-rich layers.

On this scale, a Pennsylvania or Daraflin base oil has a value of about 100, and the so-called asphalt or naphand separately recovering the nitro-isobutane petroleum origin which comprises intimately mixing therewith 2-nitroisobutane, at such temperature that two phases result, separating the two phases, and separately recovering nitroparafiin from the oil present in each phase.

3. The 'method of improving lubricating oils of petroleum origin including the steps of mixing the oil with a nitro-isobutane at such a temperature that the mixture separates into two liquid phases upon standing, separating the two phases,

from each phase.

4. The method of extracting lubricating oils of petroleum origin comprising the steps of intimately mixing theoil with a mono-nitro-isobutane at such a temperature that the mixture separates into two liquid phases upon standing, separating the two phases, and separately recovering the mono-nitro-isobutane from each phase.

5. The method of improving lubricating oils of petroleum origin comprising the steps of intimately mixing the oil with a volume of l-nitroisobutane approximately equal to double the volume of the oil and at such a temperature that the mixture separates into two liquid phases upon 2. The method of improving lubricating oils of Table H standing, separating the said two liquid phases, and separately recovering the l-nitro-isobutane e o Refractive Material 1* 0. index from each phase.

30 6. The method of improving lubricating oils of chlo-r'ex M578 petroleum origin comprising the steps of intiiirigl ig stg k -i. mately mixing the oil with a volumeof l-nitro- 1 33, 33,53,333; 4059 isobutane approximately, equal t'o'double the vol-, Znitro iso-butane 1'357T0 ume of the Oil and at a temperature of 1 1 OX1- 35 mately 70 F., permitting the oil-l-nitro-isobu- Table III V Refractive Solvent Temperature Solvent index 501- Oilrlch Per cent T 0. oil ratio vent rich layer extracted layer Chlorex (BB'-dichloro ethyl ether) 24 75.2 F.) 29% 1.4626 1.4874 2s 5 V lnitroiso-butane; 24 (75.2F.) 23 1.4220 1. 4733 I 39.3

. 6 Donn.-. 17(62.6F.) L: 1.4204 1.4105 2&6 2 nitro iso-butane 23 (734 F.) 1. 4223 1. 4676 28. 2

I claim: 4 tane mixture to separate into two liquid phases 1. The'method of improving lubricating oilsof 60' up S a ng at this said temperatu e, Separatpetroleum origin which comprises intimately mixing the two phases, and separately recovering ing therewith l-nitroisobutane, at such temperature that two phases result, separating the two phases, and separately recovering nitroparafiin from the oil present in each phase. 5

the l-nitro-isobutane from each phase for reuse.

GEORGE G. OIBERFELL. V 

